feat(library): rebuild the folder picker as a tree with a live plan

Pick folders from a lazily loaded tree with find-by-name and typed paths, beside a plan showing
the books each organization mode would import, overlaps with other libraries, and folders no
library reads yet. New ManageLibraries /path routes walk folders within entry and time bounds.
Fix the scanner filing a disc-named library folder such as /mnt/disk1 under the folder above it,
and move books already filed there onto their primary file on the next scan.

packages/types/src/path.ts

@@ -13,3 +13,95 @@ export interface CreateFolderRequest {
 }
 
 export type CreateFolderResult = DirectoryEntry;
+
+/** Why a folder could or could not be read. `blocked` is a system path BookOrbit never opens. */
+export type FolderState = "ok" | "denied" | "missing" | "blocked";
+
+export interface FolderListingEntry extends DirectoryEntry {
+  /** On a different filesystem than its parent: a Docker volume, a NAS share. */
+  mount: boolean;
+  /** An operating-system folder directly under `/` (bin, usr...), hidden unless asked for. */
+  system: boolean;
+  /** BookOrbit's own data folder (covers, caches, plugins). */
+  appData: boolean;
+  /** Whether it holds any listable folder. Null when the parent was too large to check every child. */
+  hasChildren: boolean | null;
+}
+
+export interface FolderListing {
+  path: string;
+  state: FolderState;
+  entries: FolderListingEntry[];
+  /** Only the first folders by name are listed; the rest are reached by typing a path or finding. */
+  truncated: boolean;
+}
+
+/** `pending`: the request's time ran out before this folder was walked; ask for it again. */
+export type FolderSummaryState = FolderState | "pending";
+
+/**
+ * Counts for one folder from a walk that stops at a fixed number of entries. When `truncated` is
+ * true every count is a lower bound.
+ */
+export interface FolderSummary {
+  path: string;
+  state: FolderSummaryState;
+  /** Book files: what File as Book would import. */
+  files: number;
+  /** Books as Folder as Book: one per file directly inside, plus one per folder below holding book files. */
+  folderBooks: number;
+  /** Book files per format, keyed by lower-case extension. */
+  formats: Record<string, number>;
+  /** Folders directly inside. */
+  folders: number;
+  /** Folders below holding several differently named books, which Folder as Book reads as one. */
+  mergedFolders: number;
+  /** Folders below holding several audio files, which File as Book reads as one book each. */
+  splitAudioFolders: number;
+  truncated: boolean;
+}
+
+export interface FolderSummariesRequest {
+  paths: string[];
+}
+
+export interface FolderInspection extends FolderSummary {
+  /** Size of the book files counted. */
+  bytes: number;
+  /** The first book files found, relative to the folder. */
+  samples: string[];
+}
+
+export interface FolderSearchResult {
+  results: string[];
+  truncated: boolean;
+}
+
+export interface FolderPickerLibrary {
+  id: number;
+  name: string;
+  icon: string | null;
+  type: string;
+  folders: string[];
+}
+
+export interface FolderPlaces {
+  root: string;
+  /** Folders on their own filesystem near the browse root. */
+  mounts: string[];
+  /** BookOrbit's data folder when it is inside the browse root. */
+  appDataPath: string | null;
+  /** Every library and the folders it reads, for landmarks and overlap checks. */
+  libraries: FolderPickerLibrary[];
+}
+
+export interface UnclaimedFolder {
+  path: string;
+  files: number;
+  formats: Record<string, number>;
+}
+
+export interface UnclaimedFolders {
+  folders: UnclaimedFolder[];
+  truncated: boolean;
+}